1. Field of the Invention
The present invention relates to a magnetic random access memory including a memory cell having a magnetoresistive effect element and heater layer, and a write method and manufacturing method of the same.
2. Description of the Related Art
Recently, a number of memories that store information by new principles have been proposed. An MRAM (Magnetic Random Access Memory) using the TMR (Tunneling Magneto Resistive) effect is one of these memories.
A memory cell of this MRAM comprises, e.g., an MTJ (Magnetic Tunnel Junction) element and switching element. Letting F (Feature size) be the short side of the MTJ element and 2F be its long side, the cell size is 12F2 when a MOSFET is used as the switching element. This cell size is larger than that of a DRAM or flash memory. Therefore, a method that forms a bit line for easy axis write below the MTJ element and forms a lower electrode and the fringe of this contact in self-alignment is sometimes used. In this case, the cell size decreases to 10F2, but this cell size is still unsatisfactory for micropatterning.
To implement a 256-Mbit class, large-capacity MRAM, it is necessary to decrease the cell area to about 1 μm2 or less and downsize a peripheral circuit of the cell. To decrease the cell area to about 1 μm2 or less, F of the cell design rule must be decreased to about 0.13 μm. To miniaturize the peripheral circuit of the cell and decrease the ratio occupied by the cell to about 0.6, it is essential to decrease the value of a cell write current to about 1 mA or less. When the cell width F is about 0.4 μm, however, even the smallest write current value of the presently reported MTJ elements is about 8 to 10 mA.
Note that pieces of prior art reference information related to the present invention are as follows.
[Non-patent Reference 1] M. Durlam et al., A low power 1 Mbit MRAM based on 1T1MTJ bit cell integrated with Copper Interconnects, 2002 Symposium on VLSI Circuits Digest of Technical Papers
[Non-patent Reference 2] Ikeda et al., “GMR Film and TMR Film Using GdFe Alloy Perpendicular Magnetization Film”, Journal of Japan Applied Magnetics Vol. 24, No. 4-2, 2000, pp. 563-566 [Non-patent Reference 3] N. Nishimura et al., “Magnetic tunnel junction device with perpendicular magnetic films for high-density magnetic random access memory”, JOURNAL OF APPLIED PHYSICS, VOLUME 91, NUMBER 8, 15 Apr., 2002